The asthenosphere and all areas below.
The answer is the asthenosphere, the crust is part of the lithosphere, which is part of the outer portion of the earth (the part we live on), the asthenosphere is just below it and the point where rocks begin to melt.
Melted rock in the Earth's mantle is called magma.
None of it. The most the atmosphere's heat and temperature can do is evaporate water.
Igneous rock is formed from solidified melt.
A volcano is a part of the earth where there is so much heat underground that the rocks actually melt and are forced to the surface. Volcanoes are formed of the rock that solidifies as that molten rock cools down and hardens.
In which region of the Earth's interior does the heat increase to the point that rocks can begin to melt?
When minerals melt, they can form an igneous rock called granite. Granite is typically composed of quartz, feldspar, and mica minerals that solidify from a molten state, either deep underground or at the Earth's surface.
Absolutely. If a rock is heated up by subduction into deeper parts of the earth, or even if it is in contact with other molten rocks (like lava) it can melt.
Magma is already molten rock that forms beneath the Earth's surface. It can melt other rocks, but it cannot melt elements or compounds with higher melting points, such as diamonds or tungsten.
The rock actually has to go back into the earth and melt into magma. When this magma cools off it'll emerge as either intrusive (cooled inside of the Earth) or extrusive (cooled "outside" of the Earth) igneous rock.
If heat and pressure inside the Earth cause a rock to melt, the resulting material would be magma. When magma cools and solidifies, it can form igneous rock. The composition of the magma depends on the original rock material and the conditions under which it melted.
IF the sedimentary rock is taken down deep into the earth in a subduction zone, it could melt and form lave.